This invention relates generally to the field of solar energy collection and conversion systems and more specifically to an improved solar water heating and storage system which separates the conductive solar collector fluid medium from the domestic hot water supply in such a way as to maximize the solar collector efficiency and optimize the heating and storage of the domestic hot water supply.
In these times of energy consciousness, fueled by the increased costs of natural gas, petroleum by-products and electrical power, alternative means for heating domestic water supplies are desirable. Use of radiant solar energy to heat domestic water supplies is one such alternative means which has gained widespread use in the prior art. Generally, there are presently three types of prior art solar energy devices currently being utilized for heating domestic water (i.e. both commercial and residential) supplies. Each of these systems have the following elements in common; (1) a water supply to be heated; (2) a solar collector panel and (3) a tank to store the heated water. However, each of the presently available systems process various inherent deficiencies which have detracted from their acceptance in the market place.
The first general type of prior art solar energy system inputs residential water line directly into the solar collector panel. The heated efflux from the solar collector panel is collected and stored in a conventional domestic water heater. A pump and return line from the water heater back to the collector panels is additionally typically utilized to permit the solar reheating of the stored water if needed. The domestic water heater is therefore, both the solar collector storage reservoir and the domestic water reservoir for the solar system.
In a modification of the first general type of prior art solar energy heating system, a secondary or auxiliary storage tank is positioned between the solar collector and the conventional residential water heater. The water to be heated is pumped from the auxiliary storage tank to the solar collector panel, heated and then returned to the auxiliary storage tank. As hot water is drawn from the residential water heater, supplemental solar heated water is pumped into the residential water heater.
The second type of prior art solar heating system, is generally known as a thermal siphon-system, wherein the solar collector panels are physically situated at an elevation below the storage reservoir so that the heated water within the solar collector panels will naturally rise as a result of physical forces and return to the reservoir for storage. This particular type of system requires that the solar collector panels be placed at a lower elevation than the solar collector reservoir and hence can only be utilized in limited applications.
The third type of prior art solar energy heating system, another two-tank system, has separate reservoirs for domestic hot water and solar collector fluid. The domestic water to be heated is pumped from the domestic reservoir through a heat exchange coil located within the solar reservoir, and returned to the domestic reservoir. The solar reservoir fluid, cooled by the conductive transfer of heat to the domestic water via the heat exchange coil, is pumped from the solar reservoir to the solar collector panel, heated and then returned to the solar collector reservoir.
In this third type of prior art system with the two tanks thermally connected by a heat exchanger coil, the heat losses from the tank surfaces and the inefficiency of conventional heat exchange technology result in a significant reduction in the solar collector panel's performance.
In the first two general prior art systems, the water which is eventually used for domestic purposes is run directly through the solar collector panels. As such, a problem arises since, as the domestic water is heated, its solubility quotient decreases. This decrease in solubility results in deposition within the actual solar collector unit, of minerals carried in solution by the residential water supply. As a result of this mineral deposition, periodic cleaning or replacement of the solar collector panel is continually required. Furthermore, this deposition also contributes to a continually decreasing efficiency of the solar collector itself. Chemicals which could be used to prevent this mineral precipitation cannot be added to the water coursing through the collector since the water must still be potable.
Another problem with the first two general prior art systems is the fact that the general efficiency of the solar heating system is lowered since cold incoming water is constantly mixed with heated water. This reduces the temperature of the hot water out of the system, thus requiring secondary heaters to maintain the desired temperature levels. Furthermore, such mixing increases the temperature of the water going to the collectors, thus reducing the collector efficiency. In order to maximize the efficiency of the solar collector means itself, the lowest temperature fluid should be introduced into the solar collector, since the lower the influx fluid's temperature, the lower the radiation losses at the collector. Finally, the exposure of the heated domestic water supply to ambient temperatures maximizes the absorbed heat which is re-radiated and lost to the atmosphere. In conclusion, there is a need for a solar heating system which avoids these deficiencies in a convenient manner.